Meaning of “serve” - Learner’s Dictionary

serve

verb uk us /sɜːv/
FOOD/DRINK [ I, T ]

A2 to give someone food or drink, especially guests or customers in a restaurant or bar:

We're not allowed to serve alcohol to anyone under 18.
SHOP [ I, T ]

B1 to help customers and sell things to them in a shop:

Are you being served?
WORK [ I, T ]

to do work that helps society, for example in an organization such as the army or the government:

to serve in the army
to serve on a committee/jury
He served as mayor for 5 years.
BE USEFUL [ I, T ]

to be useful as something:

It's a very entertaining film but it also serves an educational purpose.
The spare bedroom also serves as a study.
[ + to do sth ] He hopes his son's death will serve to warn others about the dangers of owning a gun.
PRISON [ T ]

to be in prison for a period of time:

Williams, 42, is serving a four-year jail sentence.
SPORT [ I ]

in a sport such as tennis, the action of throwing the ball up into the air and then hitting it towards the other player

serves one/two/four, etc

If an amount of food serves a particular number, it is enough for that number of people.

→ See also It serves her/him/you right!

(Definition of “serve verb” from the Cambridge Learner’s Dictionary © Cambridge University Press)